1. Field
The present invention relates to an MPLS tunnel identification method and device, and in particular to a method and device for identifying an MPLS tunnel used in combination with a pseudo wire.
2. Description of the Related Art
A pseudo wire (hereinafter, occasionally abbreviated as PW) is, as shown in FIG. 11, a means for offering line services such as Ethernet (registered trademark), ATM (Asynchronous Transfer Mode) and FR (Frame Relay) over an MPLS (Multi-Protocol Label Switching) network NW that is a single packet network, and is utilized as a method for realizing L2VPN.
Establishment (setup) of an MPLS tunnel (hereinafter, occasionally referred to simply as tunnel) and establishment of a pseudo wire are individually performed by using signaling (PW signaling) processes between a node (ingress node or ingress router) NI and a node (egress node or egress router) NE forming the MPLS network NW and respectively connected to customer edges CE. Mapping (combination/correspondence) of pseudo wires and MPLS tunnels is set by “Provisioning” only in the ingress node NI. Therefore, the egress node NE can not identify the correspondence (associated relationship) between the pseudo wires and the MPLS tunnels, so that monitoring the PW layers can not be performed only by monitoring the tunnel layers, incurring the following problems:
It is necessary to support OAM operations by pseudo wire in a pseudo wire layer, consuming a large bandwidth with control packets, with a result of a high load as the number of pseudo wires increases;
In the event of a tunnel layer's fault, the egress node NE having detected the tunnel fault can not identify a pseudo wire influenced by the tunnel fault, requiring a considerable time for a link down transfers.
In order to solve such a problem, there has been proposed a method wherein tunnel identification (ID) information is added to a label notification message of pseudo wire thereby to enable the egress node NE to identify the correspondence.
A related art system for thus enabling the egress node to identify a correspondence between pseudo wires and tunnels is shown in FIG. 12. For the preparation of pseudo wires, the nodes NI and NE respectively perform a label distribution for determining tunnel labels and PW labels (step S110).
Namely, upon establishing MPLS tunnels, the ingress node NI sends a label request to the egress node NE (step S100), which responsively assigns a label (step S101). Upon establishing PW labels, the egress node NE notifies a PW label to the ingress node NI with a PW label message (step S102).
The PW label message is added with PW identification information (INFO), so that it can be identified as a message relating to PW1 from the identification information. This message is notified to the ingress node NI with being also added with identification information of a tunnel (tunnel #2 in the example shown) through which PW1 is desired to be passed, so that the ingress node NI passes PW1 through the tunnel notified, thereby enabling the egress node NE to identify the correspondence.
As a reference example, there is a VLAN tunneling protocol, in which a packet is tunneled via a label-switched path (LSP) according to an MPLS protocol; at a second switching node from the last of the LSP, the present label value is replaced by a label value reserved for a packet transmitted from a port associated with the VLAN; an egress switching node of the LSP receives a packet of the label value reserved and identifies that VLAN information is embedded in the packet to extract the destination address to be transmitted to the last destination (see e.g. Japanese patent application publication 2002-247083 (US 2002/0101868A1)).
In the related art shown in FIG. 12, the notification of the tunnel identification information is performed only at the time of transmission of the PW label notification message (step S102). Therefore, as shown in FIG. 13, when a working tunnel #1 is switched over to a protection tunnel #2, the egress node NE can not identify the correct correspondence.
Namely, at the time of preparing a pseudo wire, the tunnel identification information notified together with the PW label information (PW1) indicates the tunnel #1 (working tunnel), with the result that the egress node NE identifies the correspondence between PW1 and the tunnel #1 (from PW1 to the tunnel #1). When the tunnel #1 for example is faulted and switched over to the tunnel #2, the egress node NE does not perform the label assignment and the notification of the tunnel identification information to the ingress node NI, so that the correspondence is not newly updated (step T10), resulting in the above problem left.
Thus, the above related art system has not taken into account a case where the correspondence between pseudo wires and MPLS tunnels is dynamically changed such as a case where a protection (backup) tunnel is established.